Method and apparatus for increasing a durability of a body

ABSTRACT

An inseparable assembly includes a body including a ceramic matrix composite material, and a cover including a metallic wire mesh. The cover is bonded to the body so that the cover overlaps at least a portion of the body.

BACKGROUND OF THE INVENTION

The present invention relates generally to ceramic matrix compositematerials, and more specifically to a method and apparatus forincreasing a durability of a ceramic matrix composite material.

Gas turbine engines typically include a compressor, a combustor, and aturbine. Airflow entering the compressor is compressed and channeled tothe combustor, wherein the air is mixed with a fuel and ignited within acombustion chamber to produce combustion gases. The combustion gases arechanneled to a turbine that extracts energy from the combustion gasesfor powering the compressor. One turbine extracts energy from thecombustion gases to power the compressor. Other turbines may be used topower an output shaft connected to a load, such as an electricalgenerator. In some applications, the combustion gases exiting theturbine(s) are channeled through an engine exhaust nozzle to producethrust for propelling an aircraft in flight.

Some known gas turbine aircraft engines include an engine exhaust nozzlehaving a variable geometry configuration, wherein a cross-sectional areaof the exhaust nozzle is adjustable. Variable geometry exhaust nozzlestypically have a plurality of flaps and a plurality of seals mountedcircumferentially about a centerline of the exhaust nozzle. The sealsare mounted generally between adjacent nozzle flaps, such that the flapsand seals form a generally continuous interior surface that directs aflow of the combustion gases through the exhaust nozzle. As their nameimplies, the seals seal the spaces between the flaps and shield variouscomponents of the exhaust nozzle from high temperatures and high thermalgradients during flow of the combustion gases therein.

To facilitate extending a useful life at high temperature operation,some seals are fabricated from non-metallic composite materials, such asceramic matrix composite materials. However, even such non-metallicmaterials experience wear and other damage due to the hostile operatingenvironment in gas turbine engines. For example, the seal edges mayerode due to frictional contact with the flaps as well as point contactrub caused by part deformation from the high thermal gradients the sealsexperience during operation.

SUMMARY OF THE INVENTION

In one aspect, an inseparable assembly is provided having a bodyincluding a ceramic matrix composite material, and a cover including ametallic wire mesh. The cover is bonded to the body so that the coveroverlaps at least a portion of the body.

In another aspect, a variable geometry exhaust nozzle is provided for agas turbine engine having an exhaust centerline. The nozzle includes aplurality of flaps arranged around the exhaust centerline, each of theflaps having a sealing surface, and a plurality of flap seals. Each sealhas a body which includes a sealing surface. The body is positionedbetween a pair of flaps of the plurality of flaps so that the sealingsurface of the seal engages the sealing surface of at least one of theadjacent flaps. At least one of the seals has a cover including ametallic wire mesh bonded to the body with an adhesive so that the coveroverlaps at least a portion of an edge of the body.

In yet another aspect, a method is provided for increasing a durabilityof a body including a ceramic matrix composite material. The methodincludes the steps of positioning a cover including a metallic wire meshover at least a portion of the body, and bonding the positioned cover tothe body.

Other features of the present invention will be in part apparent and inpart pointed out hereinafter.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a schematic of an exemplary gas turbine engine;

FIG. 2 is a perspective of a portion of the gas turbine engine shown inFIG. 1 illustrating a portion of an exemplary exhaust nozzle assembly;

FIG. 3 is a cross section of the exhaust nozzle assembly shown in FIG. 2taken alone line 3-3 of FIG. 2;

FIG. 4 is a perspective of an exemplary flap seal body for use with theexhaust nozzle assembly shown in FIG. 2;

FIG. 5 is a perspective of the flap seal body shown in FIG. 4 after amaterial removal process;

FIG. 6 is a cross-section of the flap seal body shown in FIG. 5 takenalong line 6-6 of FIG. 5;

FIG. 7 is a cross-section of the flap seal body shown in FIG. 5 takenalong line 7-7 of FIG. 5;

FIG. 8 is a perspective of an exemplary cover for use with the flap sealbody shown in FIG. 5;

FIG. 9 is a cross-section of the cover shown in FIG. 8 taken along line9-9 of FIG. 8; and

FIG. 10 is a perspective view of the flap seal body shown in FIG. 5having a plurality of covers, such as the cover shown in FIG. 8, bondedthereto.

Corresponding reference characters indicate corresponding partsthroughout the several views of the drawings.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT

Referring now the to the drawings, FIG. 1 is a schematic of a gasturbine engine 20 including a fan 22, a high pressure compressor 24, anda combustor 26. The engine 20 also includes a high pressure turbine 28and a low pressure turbine 30. The fan 22 and the turbine 30 are coupledby a first shaft 34, and the high pressure compressor 24 and the turbine28 are coupled by a second shaft 36. In one embodiment, the engine 20 isa F414 engine commercially available from GE Aircraft Engines, Evendale,Ohio.

In operation, air received through an inlet end 38 of the engine 20 iscompressed by the fan 22 and channeled to the high pressure compressor24, wherein the compressed air is compressed even further. The highlycompressed air from the high pressure compressor 22 is channeled to thecombustor 26, wherein it is mixed with a fuel and ignited to producecombustion gases. The combustion gases are channeled from the combustor26 to drive the turbines 28 and 30, and exit an outlet end 40 of theengine 20 through an exhaust nozzle assembly 42 to provide thrust.

FIG. 2 is a perspective of a portion of the gas turbine engine 20illustrating a sector of the exhaust nozzle assembly 42. FIG. 3 is across section of the exhaust nozzle assembly 42 taken along line 3-3 ofFIG. 2. The nozzle assembly 42 includes a plurality of flaps 70 and aplurality of flap seals 72. The flaps 70 and the flap seals 72 arearranged circumferentially around a centerline 74 of the exhaust nozzleassembly 42. Each flap seal 72 is positioned between a pair of adjacentflaps 70 and radially inwardly with respect to the flaps 70, such that aportion of each flap seal 72 overlaps a portion of each adjacent flap70. More specifically, each flap 70 includes a body 76 having a sealingsurface 78, and each flap seal 72 includes a body, generally referred toby the reference numeral 80, having a sealing surface 82. The flap seals72 overlap adjacent flaps 70 such that during operation of the engine 20a portion of each flap sealing surface 78 contacts a portion of eachcorresponding sealing surface 82 generally along an axial length of theflaps 70 and the flap seals 72. In one embodiment, the flap seal bodies80 are fabricated from a ceramic matrix composite material. In anotherembodiment, the flap seal bodies 80 are fabricated from an oxide-basedceramic matrix composite material. Additionally, in one embodiment, theflap bodies 76 are fabricated from a ceramic matrix composite material.

Respective radially inner surfaces 86 and 88 of the flaps 70 and theflap seals 72 form a generally continuous interior surface defining anexhaust nozzle orifice 90. The orifice 90 directs a flowpath of gasesreceived from the turbine 30 (shown in FIG. 1) out of the engine outletend 40 to produce thrust. In the exemplary embodiment, the exhaustnozzle assembly 42 is a variable geometry exhaust nozzle, wherein across-sectional area of the nozzle orifice 90 is adjustable. A mountingassembly, generally referred to herein with the reference numeral 92,couples each flap seal 72 to adjacent flaps 70. The assembly 92 ismovably coupled to an outer casing 94 of the engine 20 to facilitateadjustment of the cross-sectional area of the orifice 90. Additionally,the assembly 92 allows relative motion between the flaps 70 and the flapseals 72 to facilitate contact between the sealing surfaces 78 andrespective sealing surfaces 82, and to facilitate adjustment of thecross-sectional area of the orifice 90. In the exemplary embodiment, theexhaust nozzle orifice 90 is generally annular, however, it should beunderstood the orifice 90 may be any suitable shape. For example, in analternative embodiment, the exhaust nozzle orifice 90 is generallyrectangular.

During operation of the engine 20, a pressure of the flowpath gasesexiting through the exhaust nozzle orifice 90 urges the flap seals 72against the flaps 70, and more specifically, urges the sealing surfaces82 of the seals 72 in contact with respective sealing surfaces 78 of theflaps 70. As gases flow through the nozzle assembly 42, and morespecifically the exhaust nozzle orifice 90, contact between the sealingsurfaces 78 and respective sealing surfaces 82 substantially preventsleakage of gases between the flaps 70 and the flap seals 72.

FIG. 4 is a perspective of an exemplary flap seal body 80 for use withthe exhaust nozzle assembly 42 (shown in FIG. 2). Generally, the body 80includes a plurality of ends 100, 102, 104, and 106. The body 80 alsoincludes the sealing surface 82, the radially inner surface 88, and aplurality of other surfaces 120, 122, 124, and 126. Any of the surfaces82, 88, 120, 122, 124, and 126 may be designated a first surface or asecond surface. The body 80 also includes plurality of openings,generally referred to by the reference numeral 128, for attachment tothe mounting assembly 92.

FIG. 5 is a perspective of the flap seal body 80 after a materialremoval process. FIG. 6 is a cross-section of the flap seal body 80taken along line 6-6 of FIG. 5. FIG. 7 is a cross-section of the flapseal body 80 taken along line 7-7 of FIG. 5. Material is removed fromthe body 80 using any suitable machining process, such as, for example,cutting, grinding, planing, facing, and/or milling. After materialremoval, the body 80 generally includes the ends 100, 102, 104, and 106,the sealing surface 82, the radially inner surface 88, and a pluralityof mating surfaces 130, 132, 134, 136, 138, 140, 142, 144, 146, 148, and150. In the exemplary embodiment, the mating surfaces 130, 134, 138,140, 142, and 144 are generally perpendicular to the surfaces 132 and136. In addition, in the exemplary embodiment, the mating surfaces 132and 136 are generally perpendicular to the surfaces 146, 148, and 150.Any of the surfaces 82, 88, 130, 132, 134, 136, 138, 140, 142, 144, 146,148, and 150 may be designated a first surface or a second surface.

A plurality of edges 152, 154, 156, 158, 160, 162, 164, 166, 168, 170,172, and 174 extend between corresponding surfaces 130, 132, 134, 136,138, 140, 142, 144, 146, 148, and 150 of the body 80. More specifically,the edge 152 is defined at the intersection of the surfaces 130 and 132,the edge 154 is defined at the intersection of the surfaces 132 and 134,the edge 156 is defined at the intersection of the surfaces 134 and 136,and the edge 158 is defined at the intersection of the surfaces 136 and138. Similarly, the edge 160 is defined at the intersection of thesurfaces 140 and 132, the edge 162 is defined at the intersection of thesurfaces 132 and 142, the edge 164 is defined at the intersection of thesurfaces 142 and 136, and the edge 166 is defined at the intersection ofthe surfaces 136 and 144. Additionally, the edge 168 is defined at theintersection of the surfaces 150 and 136, the edge 170 is defined at theintersection of the surfaces 136 and 148, the edge 172 is defined at theintersection of the surfaces 148 and 132, and the edge 174 is defined atthe intersection of the surfaces 132 and 146.

FIG. 8 is a perspective of an exemplary cover, generally referred to bythe reference numeral 180, for use with the flap seal body 80 (shown inFIG. 5). FIG. 9 is a cross-section of the cover 180 taken along line 9-9of FIG. 8. The cover 180 includes a plurality of outer sides 182, 184,and 186, and a plurality of mating sides 188, 190, 192, 194, and 196.The cover 180 also includes end surfaces 198 and 200 generally definingrespective ends, generally referred to by the reference numerals 202 and204, of the cover 180. In the exemplary embodiment, the outer sides 182and 186 are generally perpendicular to the outer side 184, and themating sides 188 and 192 are generally perpendicular to the mating sides190, 194, and 196. The cover 180 has a predetermined durability that isgreater than a predetermined durability of a portion of the flap sealbody 80 adjacent one or more of the flap seal body ends 100, 102, 104,and 106. In one embodiment, the flap seal body 80 has a substantiallyuniform durability throughout that is less than the predetermineddurability of the cover 180.

In one embodiment, the cover 180 is a metallic wire mesh, however, itshould be understood that the cover 180 may be any material, and may befabricated in any material configuration, having a durability greaterthan a predetermined durability of a portion of the flap seal body 80,and more specifically, a portion of the flap seal body 80 that includesthe cover 180 bonded thereto, as described below. In one embodiment, thecover 180 is a metallic wire mesh fabricated from a nickel-based alloy,such as, for example, HAYNES® HASTELLOY X™ alloy, commercially availablefrom Haynes International, Inc., Kokomo, Ind. In another embodiment, thecover 180 is a metallic wire mesh fabricated from a cobalt-based alloy,such as, for example, HAYNES® alloy 188, commercially available fromHaynes International, Inc., Kokomo, Ind. In yet another embodiment, thecover 180 is a metallic wire mesh fabricated from stainless steel, suchas, for example, stainless steel grade 316 commercially available fromCleveland Wire Cloth, Cleveland, Ohio.

FIG. 10 is a perspective view of the flap seal body 80 having aplurality of the covers 180 bonded thereto to increase a durability ofthe seal body 80 generally adjacent the ends 102, 104, and 106. In theexemplary embodiment, a plurality of the covers 180 are bonded to theseal body 80. However, it should be understood that the seal body 80 mayhave any number of the covers 180 bonded thereto. For example, in analternative embodiment, the body 80 has only one cover 180 bondedthereto. Additionally, in the exemplary embodiment, the body 80 includesa plurality of the covers 180 that are each bonded to the seal body 80adjacent a corresponding end 102, 104, and 106. However, it should beunderstood that the seal body 80 may include a cover 180 bonded theretoadjacent the body end 100.

The covers 180, referred to herein as the covers 180 a, 180 b, and 180 cwith regard to FIG. 10, are bonded to the seal body 80 using anadhesive. In one embodiment, the adhesive used to bond the covers 180 a,180 b, and 180 c to the seal body 80 is a ceramic adhesive, for example,a ceramic adhesive produced by combining a glass powder, for example,SP921® glass powder from Specialty Glass, Florida, and an alumina powderwith a silica yielding polymer. Another example of a ceramic adhesive isCotronics 901® adhesive, available from Cotronics Corporation, Brooklyn,N.Y. Additionally, prior to bonding the covers 180 a, 180 b, and 180 cto the flap seal body 80, the seal body mating surfaces 130, 132, 134,136, 138, 140, 142, 144, 146, 148, and 150 are cleaned by slightlysanding the surfaces and applying a solvent, for example acetone orisopropanol, to provide a substantially wetable surface that facilitatesadhesion between the adhesive and the mating surfaces.

After cleaning, the adhesive is applied to some or all of the matingsides 188, 190, 192, 194, and 196 of each cover 180 a, 180 b, and 180 c,in addition to the seal body mating surfaces 130, 132, 134, 136, 138,140, 142, 144, 146, 148, and 150. The covers 180 a, 180 b, and 180 c arethen positioned on the seal body 80 over the respective ends 102, 104,and 106, as illustrated in FIG. 10. More specifically, the cover 180 ais positioned over the end 102 such that the mating sides 188, 190, 192,194, and 196 of the cover 180 a contact the respective mating surfaces132, 148, 136, 150, and 146 of the body 80, and accordingly, the cover180 a overlaps the seal body edges 168, 170, 172, and 174. Additionally,the cover 180 b is positioned over the end 104 such that the matingsides 188, 190, 192, 194, and 196 of the cover 180 b contact therespective mating surfaces 132, 134, 136, 138, and 130 of the body 80,and accordingly, the cover 180 b overlaps the seal body edges 152, 154,156, and 158. Furthermore, the cover 180 c is positioned over the end106 such that the mating sides 188, 190, 192, 194, and 196 of the cover180 c contact the respective mating surfaces 136, 142, 132, 140, and 144of the body 80, and accordingly, the cover 180 c overlaps the seal bodyedges 160, 162, 164, and 166. Once dry, the adhesive bonds the covers180 to the seal body 80. The greater durability of the covers 180 withrespect to the body 80 facilitates increasing the durability of the sealbody ends 102, 104, and 106 by reinforcing the body 80 adjacent the ends102, 104, and 106.

In the exemplary embodiment, the covers 180 a, 180 b, and 180 c eachsubstantially overlap the respective ends 102, 104, and 106. However, itwill be understood that the covers 180 a, 180 b, and 180 c may eachoverlap only a portion of the respective ends 102, 104, and 106.Additionally, in the exemplary embodiment, the covers 180 a, 180 b, and180 c each substantially overlap the respective edges 168, 170, 172,174, 152, 154, 156, 158, 160, 162, 164, and 166. However, it will beunderstood that the covers 180 a, 180 b, and 180 c may each overlap onlya portion of the respective edges 168, 170, 172, 174, 152, 154, 156,158, 160, 162, 164, and 166.

Although the seal body 80 is herein described and illustrated in theexemplary manner, it should be understood that the seal body 80 mayinclude any number of covers 180 each bonded to any portion of the body80 such that at least one cover 180 overlaps at least a portion of thebody 80.

The above-described cover is cost-effective and reliable for increasinga durability of a ceramic matrix composite material. More specifically,the cover facilitates reinforcing a portion of the ceramic matrixcomposite material. As a result, the cover may increase the performanceand useful life of the ceramic matrix composite material, and therebyreduce replacement costs. Additionally, the cover may increase a wearresistance and a strain to failure ratio of the ceramic matrix compositematerial, and may allow the ceramic matrix composite material toexperience higher thermal gradients without failing. In the exemplaryembodiment, the cover facilitates increasing the performance and usefullife of a gas turbine engine exhaust seal. As a result, the exemplarycover facilitates reducing a number of exhaust nozzle seals that arereplaced within a gas turbine engine to maintain a desired operationalefficiency of the engine.

Although the invention is herein described and illustrated inassociation with a gas turbine engine, and more specifically, inassociation with an exhaust nozzle seal for use with a gas turbineengine, it should be understood that the present invention is applicableto any ceramic matrix composite material. Accordingly, practice of thepresent invention is not limited to gas turbine engine exhaust nozzleseals nor gas turbine engines generally. Additionally, practice of thepresent invention is not limited to gas turbine engine exhaust nozzleseals that are fabricated from ceramic matrix composite materials.Rather, it should be understood that the present invention is applicableto gas turbine engine seals that are fabricated from materials otherthan ceramic matrix composite materials.

Exemplary embodiments of gas turbine engine exhaust nozzle assembliesare described above in detail. The assemblies are not limited to thespecific embodiments described herein, but rather, components of eachassembly may be utilized independently and separately from othercomponents described herein. Each exhaust nozzle assembly component canalso be used in combination with other exhaust nozzle assemblycomponents.

When introducing elements of the present invention or the preferredembodiment(s) thereof, the articles “a”, “an”, “the” and “said” areintended to mean that there are one or more of the elements. The terms“comprising”, “including” and “having” are intended to be inclusive andmean that there may be additional elements other than the listedelements.

As various changes could be made in the above constructions withoutdeparting from the scope of the invention, it is intended that allmatter contained in the above description or shown in the accompanyingdrawings shall be interpreted as illustrative and not in a limitingsense.

1-9. (canceled)
 10. A variable geometry exhaust nozzle for a gas turbineengine having an exhaust centerline, said nozzle comprising: a pluralityof flaps arranged around the exhaust centerline, each of said flapshaving a sealing surface; and a plurality of flap seals, each of saidseals having a body including a sealing surface and being positionedbetween a pair of flaps of said plurality of flaps such that saidsealing surface of said seal engages said sealing surface of at leastone of said adjacent flaps, wherein at least one of said seals has acover including a metallic wire mesh bonded to said body with anadhesive so that said cover overlaps at least a portion of an edge ofsaid body.
 11. A variable geometry exhaust nozzle in accordance withclaim 10 wherein said seal body comprises an oxide-based ceramic matrixcomposite material.
 12. A variable geometry exhaust nozzle in accordancewith claim 11 wherein said adhesive comprises a ceramic adhesive.
 13. Avariable geometry exhaust nozzle in accordance with claim 12 whereinsaid ceramic adhesive comprises the combination of a glass powder, analumina powder, and a silica yielding polymer.
 14. A variable geometryexhaust nozzle in accordance with claim 10 wherein said metallic wiremesh comprises at least one of a nickel-based alloy, a cobalt-basedalloy, and a stainless steel.
 15. A method for increasing a durabilityof a body comprising a ceramic matrix composite material, said methodcomprising the steps of: positioning a cover comprising a metallic wiremesh over at least a portion of said body; and bonding said positionedcover to said body.
 16. A method in accordance with claim 15 whereinsaid body further comprises a first surface, a second surface, and anedge extending between said first surface and said second surface, saidpositioning step comprising positioning said cover over at least aportion of said edge.
 17. A method in accordance with claim 16 furthercomprising machining at least one of said first surface and said secondsurface prior to positioning said cover.
 18. A method in accordance withclaim 15 further comprising the step of forming said cover such that atleast a portion of said cover has a shape corresponding to at least aportion of said body.
 19. A method in accordance with claim 15 whereinsaid cover is bonded to said body using a ceramic adhesive.
 20. A methodin accordance with claim 15 further comprising the step of cleaning saidbody to provide a substantially wetable surface prior to bonding saidcover to said body.